Data storage devices employ voice coil motors (VCM) to position an actuator assembly with great speed and precision. Current-mode drivers have long been effectively used to control the VCM. A current-mode driver requires a high-power linear amplifier and a shunt resistor for measuring the actual current delivered to the VCM.
The cost reduction of eliminating the amplifier and resistor is significant. Furthermore, as form factors keep being reduced and power and performance demands keep increasing, the power budget has become another reason to consider changing the control system from a current-mode driver to a voltage-mode driver.
However, switching to a voltage-mode driver can be problematic because the performance of a voltage-mode driver, unlike its current-mode counterpart, is significantly affected by the VCM dynamics. What is needed is a relatively simple system model approach that adaptively compensates for phase shifting of the VCM response pole frequency in relation to changes in the resistance and inductance of the VCM windings. It is to these improvement features that the embodiments of the present invention are directed.